1. Field of the Invention
The present invention relates to a clamping device for use in an assembly process of a workpiece such as a motorcycle engine in which the workpiece is supported on a work bench, and more particularly to an efficient clamping operation. The clamping operation includes both movements for clamping and unclamping the wirkpiece.
2. Description of the Prior Art
A clamping device for a motorcycle engine is disclosed in Japanese Unexamined Patent Publication No. SHO 59-169739 (1984) in which a pair of clamp pawls for supporting the engine from both sides is provided. In this prior art, one clamp pawl is fixedly secured and the other clamp pawl is movably provided. Accordingly, even though a size of an engine supporting section is changed, the pair of clamping pawls can be used in common by adjusting the clamp pawl on the movable side.
Since the positional adjustment of the clamp pawl on the movable side is computer-controlled, the clamping device becomes complicated and expensive. It is therefore desirable that a device with a comparatively simple construction be provided in which the clamping operation can be efficiently performed by a manual operation. It is therefore an object of the present invention to meet such requirements as described above.
To solve the problems, a clamping device according to the present invention has a clamping section for clamping a workpiece movably provided on a guide shaft in the axial direction and is characterized in that a locking section for fixedly securing the clamping section in position on the guide shaft is provided to move on the guide shaft in a locking direction and in a unlocking direction and that the locking section forms a one way mechanism whereby when the locking section is moved in the locking direction, it prevents only the movement of the clamping section in the unclamping direction relative to the workpiece and when the locking section is moved in the unlocking direction, it makes the movement of the clamping section free.
In this case, the one way mechanism can be composed of an inclined plane formed on one side of fitting sections in which each part of the clamping section and the locking section is fitted into one another in a relatively slidable manner, a supporting recession long in the axial direction of the guide shaft formed on the other side facing the inclined plane, a lock ball housed in the supporting recession to axially move between the inclined plane and the guide shaft, a first spring adapted to bias the lock ball in the locking direction, and a second spring adapted to bias the locking section in the locking direction relative to the clamping section.
In the present invention, when the clamping section is manually moved on the guide shaft to move the locking section in a locking direction in a clamping position of a workpiece, only the movement of the clamping section in the unclamping direction is prevented to be in a locking position.
Further, in this locking position, if the locking section is moved in the unlocking direction, locking by the one way mechanism is released to allow the clamping section to move on either side in the axial direction of the guide shaft. In this manner, support or release of the workpiece can be effected in a single operation. Thus, it is possible to realize a clamping device with a relatively simple construction at a low cost. It is also possible to improve a working efficiency in a clamping operation.
Further, the one way mechanism comprises the inclined plane provided on one side of the fitting sections, the supporting recession provided on the other side thereof, the lock ball housed in the supporting recession, the first spring for biasing the lock ball in the locking direction, and the second spring for biasing the locking section in the locking direction. Accordingly, once the locking section is released, it is moved in the locking direction by the second spring to push the lock ball against the inclined plane, thereby bringing the one way mechanism into a locking condition. On the contrary, if the locking section is pulled in the unlocking direction against the second spring, the lock ball is separated from the inclined plane to bring the one way mechanism into an unlocking condition, thereby unclamping the lock ball by a single operation.